Heretofore, in the early detection of cervical cancer and precancer, two methods were used: cytology and colposcopy, which is the examination of the cervix by means of an endoscope. Each method has its particular limitations and strengths in cancer detection and both methods complement each other.
Although cytology is generally recognized as the most practical and economical screening method for cervical cancer, in the last ten years, colposcopy has achieved wide recognition as a valuable tool in the clinical diagnosis of patients with abnormal cytology. Unfortunately the key for success in colposcopy is determined and limited by the expertise of the examiner. The training in colposcopy is time consuming and expensive, but without proper training it is impossible to achieve adequate results. As a result, the use of colposcopy as a screening tool has been limited by lack of suitable examiners.
A further limitation of colposcopy is that colposcopical findings are recorded in a written description of the vascular and tissue pattern of the cervix. Therefore, there is no opportunity for an objective review of the documentation of the findings. In addition, colposcopy in the hands of the inexperienced physician can result in the mis-diagnosis of a cervical lesion which can endanger the life of the patient from an invasive cancer.
Although it is generally recognized that the simultaneous use of cytology and colposcopy could effectively increase the accuracy of cervical cancer detection, nonetheless, colposcopic screening has been considered impractical and uneconomical.
In 1955, the use of stereoscopic colpophotography for cervical cancer screening was suggested. However, the use of colpophotography for screening or for evaluation of patients with abnormal cytology has proven to be difficult or even impossible for the following reasons: (1) the cost of a photocolposcope is high; (2) the depth of focus is small; (3) it is difficult technically to obtain good sharp pictures because the photography is done through the oculars of the colposcope and even a minor change or refractive error can result in a blurred picture; (4) the magnification is high, and therefore, it is necessary to prepare several pictures to cover the entire cervix; (5) the colpophotography must be done by a physician experienced in colposcopy, because he must select the proper area for colpophotography. For these reasons, colpophotography has never been used on a large scale.